1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine airfoil with multiple impingement cooling.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, a fuel is combined with compressed air to create a hot gas flow that is passed through a turbine to drive a rotor shaft. In an industrial gas turbine engine, a typical four stage turbine provides the mechanical power to drive the rotor shaft, which drives the compressor and an electric generator to produce electrical power. The efficiency of a gas turbine engine can be increased by passing a higher temperature flow into the turbine. However, the turbine inlet temperature is dependent upon the material capabilities of the turbine, especially the first stage stator vanes and rotor blades.
One way to allow for higher turbine inlet temperatures is to provide cooling for the hotter airfoils. A combination of internal convection cooling, impingement cooling and film cooling on the exterior airfoil surfaces have been proposed to allow for higher flow temperatures.
Since the cooling air used for the turbine airfoils is bled off from the compressor, this work performed to compress the air is not available to perform work in the turbine. Thus, another way of increasing the efficiency of the engine is to use a minimum amount of cooling air while also providing the maximum amount of cooling with this cooling air.